1. Field of the Invention
The invention relates to a transducer which transforms the mechanical position of an aircraft control surface such as a horizontal stabilizer into an electrical signal for use in other aircraft subsystems. The invention is particularly applicable to retrofit installation into aircraft which were not originally designed to have such electrical outputs.
2. Description of the Prior Art
The position of the aircraft's horizontal stabilizer surface is generally controlled by electric or hydraulic actuators. In a typical electric actuator installation, the position is determined by an irreversible jackscrew which is turned by either of two motors, remotely operated by switch inputs from the pilots in the cockpit. Further inputs to the stabilizer jackscrew are provided by hand-operated wheels which are conveniently located to the Captain and the First Officer in the cockpit. These wheels rotate a relatively large number of turns to cover the full range of stabilizer operation and are connected to the jackscrew by cabling from the cockpit to the rear of the aircraft where the stabilizer is located. The cockpit wheels rotate whenever there is an input to the jackscrew, whether electric or manual; thus, providing a positive visual cue to the pilots that the stabilizer is moving. Since the wheels rotate many turns over the full range of stabilizer movement, it is also necessary to provide a limited range visual displacement cue to the pilots. This takes the form of mechanical displacement of a pointer covering an arc of about 40 degrees, corresponding somewhat linearly with a stabilizer movement of about 17 degrees. In older aircraft there was no requirement for an electrical output which reflected the position of the horizontal stabilizer. With the advent of new requirements such as retrofit of windshear detection devices, it is necessary to provide such electrical signals, which are difficult to obtain because of very crowded conditions that exist in the pedestal control stand between the Captain and First Officer.
The present invention adapts an existing quadric-chain pointer drive mechanism to actuate an electrical transducer which is remotely located. It provides a substantially linear rotation range of about 35 degrees with a corresponding signal output with minimum modification of the existing mechanism.